I was just reading that Dreamsleeve stuff and I was wondering...
What's the difference between the Dreamsleeve bringing you back to the mortal realm and a Necromancer bringing you back to the mortal realm?
Necromancers, I believe, trap other souls in soulgems to raise skeletons or the like. If a person dies without being soul trapped, then their soul is released into the dreamsleeve. Necromancer's can raise people's corpereal bodies from the grave, but the soul is or has been recycled (excluding if it had been soultrapped, as you can raise a person's body with that person's soul).
Another interesting fact about the Dreamsleeve, it is believed that each person sees the Sleeve as they expect it to be. The Nords see a Valhalla like place, while the other races experience different things.
Of course, on notable exception is when a mortal gives themselves up to a certain Daedric prince, as in the case of Umaril the Unfeathered. This sends the mortal's soul to that Deadra's realm when they die.
I wouldn't go so far to say the past life of a soul doesn't affect it's present/future, as in some cases it would/does, such as with Nerevar/Nerevarine.
I believe that was more divine intervention, with Azura taking Nerevar's soul and guiding the new body through the events of the Nerevarine. But I could be wrong :shrug: